Discharging successive rounds from a firearm consumes ammunition. It would be advantageous to indicate a low ammunition condition to the user of a firearm. A low ammunition indication is potentially life saving to a law enforcement officer, soldier or responsible citizen engaged in a needed use of the firearm, for example during a firelight against hostile forces.
Semiautomatic firearms often have a feature to lock the slide open upon discharge of the final round from a magazine, providing an indication of zero ammunition remaining. An indication of low ammunition prior to the condition of zero ammunition allows the user of a firearm to conserve remaining rounds and plan for reloading. Counting and attempting to remember the number of shots fired is well-known to be a difficult and unreliable method to apply in an intense situation. To remedy this difficulty, various devices are known for indicating low ammunition in a firearm.
U.S. Pat. No. 5,642,581 MAGAZINE FOR A FIREARM INCLUDING A SELF-CONTAINED AMMUNITION COUNTING AND DISPLAY SYSTEM, to Herold et al. discloses a magazine for a firearm with electrical contacts corresponding in number to the number of rounds of ammunition capable of being loaded into the upper portion of the magazine. The magazine follower has a sliding contact, which connects to a particular electrical contact in the magazine corresponding to a number of rounds remaining in the upper portion of the magazine. A seven segment LED display shows a digit indicating the numerical count of rounds of ammunition within the magazine. Alternatively, LEDs indicate a number of rounds. The LED display or LEDs are positioned in the lower part of the magazine, viewable by the user of the firearm.
U.S. Pat. No. 5,052,138 AMMUNITION SUPPLY INDICATING SYSTEM, to Crain discloses a magazine for a firearm with electrical contact strips in pairs along opposing side walls of the magazine. The magazine follower makes contact with the contact strips, providing a count of the number of cartridges or rounds present in the magazine. A display housing on the body of the pistol has a numerical display visible to the user. Wires, contacts and electronic circuitry convey and combine various signals to operate the display.
U.S. Pat. No. 5,592,769 AUTOMATIC CARTRIDGE MONITORING AND INDICATOR SYSTEM FOR A FIREARM, to Villani discloses various magazine follower mechanisms contacting various switch mechanisms in the grip of the firearm, in multiple embodiments of a cartridge monitoring system. The follower mechanisms are installed on the follower of a firearm magazine or in an intermediate device between a first spring and a second spring in the magazine. An indicator device has three LEDs of different colors positioned near the top of the grip, and each LED energizes to indicate 3, 2 or 1 cartridge left. Alternatively, a mechanical indicator moves as cartridges are expended.
U.S. Pat. No. 5,735,070 ILLUMINATED GUNSIGHT AND LOW AMMUNITION WARNING ASSEMBLY FOR FIREARMS, to Vasquez et al. discloses an illuminated gunsight and a low ammunition warning assembly, which uses a vibratory system to indicate a low ammunition condition. In one embodiment, electrical contacts are associated with a prong mounted to the internal structure of a gun. The contacts and the prong detect the presence or absence of a round at the top of the magazine. When the last round exits the magazine, the vibratory system is activated. In another embodiment, electrical contacts detect the movement of the rack structure of the gun. An electronic circuit device programmed with the total number of rounds can subtract for each motion of the rack structure and determine when the rounds of ammunition remaining in the magazine have reached a predetermined amount, and then activate the vibrating motor in the gun handle.
Existing devices often have modifications to the firearm as well as to the magazine, and require electrical connection between the firearm and the magazine. It is an object of the present invention to provide a device for indicating low ammunition in a firearm.